EXTRUDE - is this the best way to simulate separate wooden planks on vertical face
I found using an ARRAY solved my problem.
I created an array with a count of 2 on the Z axis with an offset large enough so that I could see the 2 separate objects one above the other.
I then selected the bottom object and added a material
Then I unwrapped the object and used the UV editor to ensure all faces were horizontal.
Next I set the UVs Offset U to 0.1 to ensure the 'pattern' from my material texture image was slightly different on the object above.
Lastly I moved the two objects in the array back together.